Add the chicken, onion, garlic, chipotle, cumin, black pepper, chili powder, and salt to the bowl of a large slow cooker. Pour beer over the top and cover with the lid.
Cook on low for 6-8 hours or on high for 4-5 hours until the chicken is completely tender and shreds easily with a fork.
Once the chicken is cooked, preheat your broiler to high heat (550 degrees F) and mist a large baking sheet with cooking spray. Use a fork to shred the chicken into bite-sized pieces, placing on the prepared baking sheet. Spread chicken into an even layer. Reserve liquid remaining in the slow cooker.
Place baking sheet under the broiler, 2 racks down from the very top, and broil for about 5-6 minutes, or until the edges of the chicken begin browning and crisping up. Remove the sheet from the oven. Drizzle ½ cup of the reserved liquid over the chicken; toss to coat and spread into an even layer. Broil an additional 5 minutes and repeat with ½ cup broth and an additional 5 minute broil.
Squeeze the juice of 2 limes over the top of the meat; toss. If meat seems a bit dry, you may add additional reserved liquid and toss. Serve immediately with desired toppings.